Cascaded coaxial cable transformer



July 27 1965 l. K. DOR-rom' 3,197,723

CASCADED COAXIAL CABLE TRANSFORMER Filed April 26, 1961 4 Sheets-Sheet 1g2 EI- f5..

Mirra/@ri July 27, 1965 l. K. Dom-0R1- 3,197,723

` CASGADED COAXIAL CABLE TRANSFORMER Filed April 26. 1961 4 sheets-sneet2 wQQQQQ QQQQ Jly 2.7, 1965 l. K. DoR'roR-r- 3,197,723 n cAscAnEDcoAxIAL CABLE TRANsFoRMER Filed April` 2e, 1961- 4 sheets-sheet s IWI@Mummia/M0@ l. K. DORTORT CASCADED COAXIAL CABLE TRANSFORMER July 27,1965 Filed April 26, 1961 4 Sheets-Sheet 4 INVENTOR United States PatentO M 3,197,723 CASCADED CGAXIAL CABLE 'IRANSFURMER Isadore K. Dortort,Philadelphia, Pa., assigner to EJE-E Circuit Breaker Company,Philadelphia, Pa., a corporation of Pennsylvania Filed Apr. 26, 1961.,Ser. No. 165,690 3 Claims. (Cl. 336-I95) My invention relates to a novelcascaded coaxial cable transformer construction for obtaining a veryhigh ratio transformer having a substantially zero leakage reactancewhere multi-conductor coaxial cables are used for the windings, and morespecifically relates to a novel cascading arrangement which minimizesthe number of coaxial conductors required for the cable.

In copending application (C4588) Serial No. 808,520 now abandoned, ledApr. 23, 1959, entitled Zero Reactance Transformer, in the name ofJensen and Dortort, and assigned to the assignee of the presentinvention, a transformer construction is disclosed where, by making thetransformer windings of coaxial cable, the reactance of the transformeris made substantially zero. Such transformers are highly desirable inapplications of pulse transformers to high energy pulse generators, andtransformers for short circuit generators for testing high power circuitbreakers.

When such coaxial cable transformers are manufactured, in order toobtain very high voltages, the coaxial cable must either contain a largenumber of conductors which makes it dilicult and expensive tomanufacture, or very high voltages must exist between a limited numberof adjacent conductors which also leads to great expense and diiculty inmanufacturing because of difficult insulation problems. Which ever ofthe methods is used to obtain the high output voltage, it becomesnecessary to increase the outer diameter of the cable, since either moreturns or more insulation is necessary. This increases the bending radiusof the cable and, therefore, increases the internal diameter of thecoil.

The principle of the present invention is to provide a novel transformerconstruction using the coaxial cable concept of the above notedapplication where a limited number of coaxial conductors may be usedwith a relatively -low voltage appearing between adjacent conductors,although very high voltages are obtained from the system. Morespecifically, I have found that by cascading a plurality of suchtransformers, I can obtain extremely high voltages while theconstruction of the individual transformer cables is kept withinreasonable limits. By way of example, in cascading two transformers, theinput voltage is applied to a primary winding portion of the firsttransformer. An end portion of the secondary winding of the firsttransformer, which has the same voltage appearing thereacross as theprimary voltage, is then connected to the primary winding of the secondtransformer. The total voltage output is then taken from the secondarywinding of the first transformer and the secondary winding of the secondtransformer whereby, a voltage equal to the full voltage output of thesecond transformer plus the voltage across the secondary winding of theiirst transformer, less that portion used as an input for the secondtransformer, is obtained.

This increased voltage ratio between the total output of the combinedtransformers to the voltage input of the first transformer is thusachieved without requiring an excessive number of turns kfor the coaxialcable of either of the transformers, and without requiring excessivevoltages between the adjacent conductors of the individual transformers.

In order to increase the voltage level to whatever value is required, itwill be apparent that as many transformers as necessary can be cascadedwith one another Caf) lflz Patented July 27, 1965 ICC where the input toeach successive transformer is derived from a portion of the secondaryoutput of a preceding transformer.

Accordingly, a primary object of this invention is to provide a novelhigh voltage transformer system.

Another object of this invention is to provide a novel arrangement ofcascaded coaxial cable transformers which reduces the required diameterof the coaxial cable.

Another object of this invention is to provide a novel, relativelyinexpensive high Voltage transformer.

A further object of this invention is to provide a novel high voltagetransformer system having substantially zero reactance wherein thediameter of the coaxial cable used is relatively independent of thevoltage ratio to be obtained.

These and other objects of this invention will become apparent from thefollowing description when taken in connection with the drawings inwhich:

FIGURE 1 illustrates a typical two-winding transformer formed of coaxialcable.

FIGURE 2 illustrates the coaxial cable transformer of FIGURE l as anauto-transformer.

FIGURE 3 illustrates the composite cable to be used in the embodimentsof FIGURES 1 or 2 when formed of spiral wound, round conductors.

FIGURE 4 illustrates the manner in which the coaxial winding can beformed by metallic tapes.

FIGURE 5 illustrates the manner in which the conductors of FIGURES 3 and4 can be modified with a central tubular conductor which is adapted toconduct a cooling medium.

FIGURE 6 shows another manner in which the cable of FIGURE 3 could beformed so as to conduct a coolant therethrough.

FIGURE 7 schematically illustrates the novel cascading arrangement ofthe present invention for transformers of the type shown in FIGURE 2.

FIGURE 8 schematically illustrates the manner in which the threetransformers of FIGURE 7 can be formed on a common core.

FIGURE 9 shows an enlarged view of the cascaded circuit portion ofFIGURE 7 where a portion of the secondary winding of a precedingtransformer is connected to the primary winding of a succeedingtransformer.

FIGURE 10 illustrates the manner in which the invention may be appliedto a unitary package of conductors not coaxial with one another forapplications where some minimum leakage ield is permissible.

FIGURE 1l schematically illustrates a modification of the arrangement ofFIGURE l0.

FIGURE 12 schematically illustrates a further embodiment of theinvention using a multi-layered sandwich of sheet metal and foilseparated by sheets of insulating material where the primary andsecondary windings are interleaved.

FIGURE 13 schematically illustrates a typical prior art type of.autotransformer construction.

FIGUR-E 14 schematically illustrates the novel transformer of theinvention ,as shown, `for example, in FIG- URES 7 and 9 for purposes ofcomparison with the prior art type of autotransformer construction ofFIGURE 13.

Referring now to FIGURE 1, a transformer core 20, which is constructedin accordance with the usual techniques, has a window 22 which receivescomposite winding 24 which is formed in accordance with the Iteachingsof above noted .application Serial No. 808,502.

The composite winding 24, as is schematically illustrated, has seventurns and is formed of four physically parallel `conductors 26, 28, 30and 32. These individual physically parallel conductors 26 Athrough 32are contained in an insulating -medium 34 and are insulated from oneanother, as will be seen more fully hereinafter, andsa are surrounded bya hollow conductive sheath 36 which acts as a primary winding for thetransformer. The sheath 36 is then covered with an insulating sheath 3Swhich insulates adjacent turns ofwinding 24 from one another.

As schematically illust-rated to the left of FIGURE 1, an A.C. generator40 is connected across the primary winding 36. The physically parallelconductors 26 through 32 form the secondary winding and are externallysequentially connected in series so that the secondary winding iscomprised of four times seven, or twenty-eight turns. Therefore, if thegenerator voltage is V, the output secondary voltage is 4V. Thisconnection of the individual conductors of the secondary winding is morespecifically seen in FIGURE 1 to runas follows:

The first terminal of conductor 26 forms the lower ter- -minal 42 of thesecon-dary winding. Conductor 26 then is taken through the seven-turnwinding and emerges at the top of the winding and is then externallyconnected to thelower end of conductor 281 Conductor 23 then runsthrough the seven turns of the winding and emerges at the lupperport-ion of the winding, and is then connected to the lower end ofconductor 3f). Conductor 30 then 'runs through the seven-turn windingand emerges at the upper part of the coil, and is thereafter connectedto the lower end lof conductor 32. Conductor 32 finally runs through theseven-.turn winding to complete the twentyeight turn secondary andthereafter emerges at the top of the winding, and is terminated at upperterminal 44.

Accordingly, a step-up transformer is provided in which the leakagereactance, because of the configuration of the windings, issubstantiallyzero.

The above FIGURE 1 schematically illustrates the transformer structureas a two-winding transformer. If desired, Ian auto-transformerconnection may be used to increase the economy of the unit. This isillustrated in FIGURE 2 which further specifically illust-rates thepreferred winding as formed of concentric conductors for the physicallyparallel conductors of the Winding.

In FIGURE 2, winding 24V is. formed of concentric conductor elements 46,48, 50 and 52 which correspond to conductors 26, 28, 30 and `32respectively of FIGURE 1. The generator 50 in FIGURE 2 is connectedacross the first tubular conductor 46 which serves `as the primary ofthe auto-transformer shown. The secondary winding is formed by theexternal connections between conductors 46 through 52 and starts at thelower end of conductor 46 and runs to the upper end of conductor 46 toform the i-rst seven turns. The upper end of winding 46 is thenconnected .to the 4lower end of winding 48, and the connection thenagain goes through the seven-turn Winding to the upper end of winding48. T-he upper end of winding 48 is then connected to the lower end ofwinding 50 which again goes 4through the seven turns to emerge at theupper end of winding 5t). The upper end of winding 50 is then connected`to the lower end of winding 52 which goes through the seven-turnwinding to complete the twenty-eight turns, and the conductor emerges atthe upper end of winding 52.

As was the case in FIGURE 1, the upper end of winding 52 emerges toterminal 44, while the lower end of winding 46 emerges as terminal 42.Similarly, the complete composite cable is covered with an insulatingsheath 38, while the various concentric conductors are insulated fromone another in any desired manner.

In forming lthe composite conductors of FIGURES 1 and 2, many techniquesmay be employed.

In FIGURE 3 a typical possible construction is shown where the cable ismade of spiral wound, round conductors. In this case, the innermostconductor 52 of FIG- URE 2 is seen in FIGURE 3 as being formed by theinnermost group of spiral wound, round conductors 52. Innermostconductor 52 is then covered with an insulation medium 54, and a secondlayer of spiral wound, round conductors 50 forms the conductor 50 of.FIG- URE 2. Once aga-in, an insulating sheath 56 is wound on conductorSil, and the concentric wound, round conductor layer 43 is wound oninsulation `|56. A further sheath of insulation -53 is wound on top ofconductors 4S, and sheath 5S supports the final layer of conductors 46which form the outermost tubular conductor 46 -of FIGURE 2. The completeassembly is then covered by insulation sheath 69 so that the completecomposite conductor is formed.

While FIGURE 3 shows the use of spiral wound, round conductors forforming the conductive elements, a metallic tape may be used instead ofthe round wires, as is schematically illustrated lin FIGURE 4.

In FIGURE 4, the conductive elements 46, 48 and 50 are of metallic tape,while the innermost conductor 52 may be a round conductor. As was thecase in FIG- URE 3, the conductive layers are insulated from one an-`other by insulator layers 54, 56 and 58 with insulating sheath 64Bcompleting the cable.

FIGURE 5, which is a cross-sectional View of a conductor similar to the`conductor of FIGURE 3, further illustrates that the central conductor52 can be formed of a tubular conductor where the tube may be used toconduct a cooling mediumv such as oil to carry away the internal heat ofthe conductor.

The `insulation between the various conductive layers of FIGURES 3, 4and 5 has been described as being of any desired type. Thus, it may bein the form of an extruded plastic jacket, a wound paper tape, or acloth or plastic tape, or any of the well known and commonly usedinsulating materials. Certain plastic materials, such as polyethylene,can be irradiated after the coil is formed to provide greater electricalstrength. Insulation over the sheath conductor to `form layer 60 can bein the form of `an extruded plastic, varnish, enamel, glass or clothtape. It need only be sufficient to withstand the turnto -turn voltageof the transformer :secondary winding, and have sufficient mechanicalstrength to withstand the coil winding operation.

For very high voltages, it has been found that paper insulated cable incombination with high or low pressure loil systems is suitable for theloperation of the system. This `lends itself, as is shown in FIGURE 6,to using a sheath 62 which may be of aluminum over the type of cableshown in FIGURE 3. The composite conductor may then be impregnated with-oil which is contained by lsheath 62. The aluminum sheath issubsequently surrounded by another insulating wrapping 64 to preventshort circuiting of the -turns when the winding is wound. Thetransformer may then be made essentially a dry type transformer even forvery high voltages, with the oil being contained within the cable. Thecentral conductor can readily be `formed with channels to permit therapid equalization of oil pressures.

Since the jacket 62 isa conductive member, it is clear that it could beused as another winding of the secondary, or as a primary winding.Furthermore, instead of being formed as a sheath, it may bedesirablethat it be formed of a -stranded conductor with the entire core and coilimmersed in a tank of insulating oil, as is well known in the a-rt.completely dry, it is clear that it can be enclosed in a hermeticallysealed case which would contain some inert gas, or some high dielectricgas, such as sulphur hexa uoride.

It is obvious that the low voltage primary winding will have the largestcross-section. If, as in most cases, it is desirable to tap the highvoltage winding, the current ratings of the internal conductors will begraded according to the current they will deliver at their tap. If a tapis provided at each conductor terminal, the grading will be uniform andachieved naturally by the increasing.

diameter of the conductor.

In the case of a test transformer, the duty cycle is extremely short andthe cross-section of each conductor is so dimensioned that the totalheat generated in the Still further, if the transformer is to be madeconductor during the test will raise the temperature of the conductor toa maximum safe value.

In accordance with the present invention, and in order to reduce thenumber of conductors in the coaxial cable as well as the voltage betweenthe conductors, I have discovered that I can cascade several coaxialcable transformers, as shown in FIGURE 7. Referring to FIGURE 7, I haveschematically illustrated three transformers 100, 101 and 102 which mayeach be of the type shown in FIGURE 2.

The full output voltage of the system is VN, while the input voltage isV. The bottom line 103 schematically illustrates the reference potentialof the system. It is seen that transformer 101 must be insulated fromthis reference, as schematically illustrated byinsulator 104, which iscapable of withstanding somewhat less than the full output voltage oftransformer 100, and is approximately one-third of the full outputvoltage. Transformer 102 must be insulated from ground 103, asschematically illustrated by the two insulators S and 106 which arecapable of insulating apotential of the order of twothirds of the fulloutput voltage of the system.

Each of the auto-transformers 100, 101 and 102 have respective primaryor input winding portions 107, 108 and 109. The outer end of thesecondary windings of transformers 100 and 101 have output portions 110and 111 respectively which are connected to the primary windings orinput winding portion of the succeeding transformers, whereby outputwinding portion 110 is connected to input winding 108, while outputwinding portion 111 is connected to input winding 109.

The winding portions 110 and 111 are arranged to have a voltagethereacross equal to the primary voltage V of the system, whereby eachof the cascaded transformers 100, 101 and 102 sees the same primaryvoltage.

Assuming, for the embodiment 0f FIGURE 7, that the conductor used inwinding transformers 100, 101 and 102 is a four-conductor coaxial cable,there will be provided a transformation ratio of ten to one between theoutput voltage VN and input voltage V. That is to say, the outputvoltage VN is equal to the sum of the full winding voltage oftransformer 102 which is four times as great as its input voltage plusthe voltage appearing across the winding of transformer 101 up to andexcluding winding portion 111, which is equal to three times the inputVoltage plus the voltage appearing across transformer winding 100 up toand excluding winding portion 110 which is again equal to three timesthe input voltage V.

Moreover, the transformation ratio, shown above to be ten to one, isachieved with only one-tenth of the output voltage appearing between theadjacent conductors of -any of the transformers. It will be noted thathad a single transformer having a four-conductor cable been used, thevoltage between conductors would necessarily be one-fourth of the outputvoltage rather than the onetenth obtained with the novel cascadedsystem.

Again, if a single transformer were used and were designed so that onlyone-tenth of the total voltage between conductors appears as in thenovel system of FIGURE 7, it would require the use of a ten-conductorcoaxial cable. Thus, in the case of attempting to use a singletransformer of the type shown in FIGURE 2, an attempt to achieve theresults of the system of FIGURE 7 would require a substantiallyincreased diameter for the coaxial cable, due either to a requiredincrease in insulation between the cable conductors because of theincreased voltage between conductors or an increased number of turns,due to the required turns ratio which must be met.

In FIGURE 7, I show the result of a ten to one ratio using only threetransformers which are cascaded with one another. It will be apparentthat other cascading arrangements could be used. By way of example,twoconductor coaxial cable transformers can be used where ninetransformers of this type are cascaded so that only one-tenth of theoutput voltage appears between adjacent conductors. The determination ofthe size of the transformers may be begun here by considering the totalrating of all of the transformers expressed in terms of an equivalenttwo-winding transformer. Thus, the total KVA expressed as KVAT will beequal to VI iiNet-DWH) KVATooo Ntn-nM-l-i where V is the input voltageof the primary Winding of transformer 100,

I is the input primary current of transformer 100,

N is the total number of transformers, and

n is the number of conductors in each of the coaxial cables In thegeneralized situation, it will be seen that the VA rating of the Kthtransformer is VI (ri-1) (N-K-I-l) KVM-1000 Noz-n+1 From the above, itis seen that the total KVA parts of the cascaded transformers expressedin terms of an equivalent two-winding transformer increases as thenumber of transformers increase.

While in FIGURE 7 I have illustrated my novel cascading system for thecase of three independent transformers, the same results may be obtainedin a unitary transformer construction wherein a common core is used forall of the transformers to form a multi-Winding transformer. Such aconstruction is schematically illustrated in FIGURE 8 where atransformer core 120 receives six layers of Windings schematicallyillustrated by layers 121 through 126. Each of layers 121 through 126 asshown in FIGURE 8 is formed of the four coaxial cable conductor which isused here for purposes of illustration. Equating this to FIGURE 7,layers 121 and 122 serve as a first transformer system, layers 123 and124 serve as a second transformer system, and layers 125 and 126 serveas the third transformer system. These three transformer systems are, ofcourse, fully equivalent to transformers 100, 101, and 102, respectivelyof FIGURE 7.

Clearly, each of the transformer systems can be formed of any desirednumber of layers, two layers being selected here for purposes ofillustration. In the event that an odd number of layers are used foreach section, it would be preferable to make the cable terminationsoutside of the coil area so that the cable ends or the cross connectionsbetween the ends need not be carried through the coil to produceunnecessary complications in the insulation structure.

The inter-connections between the various coils are schematicallyillustrated in FIGURE 8 where the circuit diagram achieved through suchconnections is identical to that previously shown in FIGURE 7.

It will be noted that the layer insulation between sections such as theinsulating layers 127, 128 and 129 illustrated in dotted lines for thelayer insulation between the layers of given sections or transformergroups, may be calculated in the standard manner on the basis of theoutside conductor voltage only. The barrier insulation illustrated bythe double dotted lines, such as barrier insulation layers 130 and 131,are equivalent to insulators 104 and insulators 105, respectively ofFIGURE 7, and are designed to withstand approximately volts. Theinsulation equivalent of insulator 106 is not required.

As is illustrated in FIGURE 7 and reproduced on an enlarged scale inFIGURE 9, there is a closed circuit at the point at which adjacenttransformer sections are connected. Thus, in FIGURE 9, winding portion110 is connected in closed circuit arrangement with respect to windingportion 108. It has at least partially been this closed winding portionwhich for many years has led those skilled in the art to not adopt suchan arrangement in low reactance applications, since it was felt thatthis arrangement would lend itself to substantial leakage fields. Ihave, however, found that this is not the case and have demonstratedthat practically all leakage fields are cancelled in this area.

More specitically,V if the current divides between winding portions 110and 108 merely as a function of their respective resistances, themagnetic ields of these currents in a given coaxial cable would not becancelled. Such a current distribution is shown in FIGURE 9 as 1/zInbased on the assumption that the two conductors have equal resistancesand their currents are equal. The circulating current i is caused, byreactance and proxmer winding currents in the two connected sectionswhich cause all the llux to Vcancel if so that X is again O.

These currents, however, will not divide merely according to theresistances of the windings, but there will be a circulating currentbetween them which is equivalent to the eddy current elfects found inmultiple strands of conductors of standard transformers, if woundwithout transpositions. In this particular instance, these eddy currentsare desired and necessary. They are more specilically produced by theresultant leakage field, and will produce winding currents asspecifically shown in FIG- URE 7 with only a slight error due to theresistance drop ofthe cable in the sections involved, thereby causingthe leakage fields to be essentially cancelled.

It can be demonstrated that in coaxial cables with relatively smallinsulation thickness between the conductors, this error is negligible.As a result, the coaxial currents are completely balanced just as in thecascaded transformers of FIGURE 7, so that substantially all of theleakage fields are cancelled out again to retain the exceedingly low orsubstantially zero reactance vof the cascaded transformer system.

The foregoing discussion of the operation of the novel transformer ofthe invention can be further facilitated by the comparison shown inFIGURES 13 and 14 of a standard prior art type of autotransformer andthe novel transformer of the invention schematically shown in FIGURE 14.

In each of the figures, there is illustrated a common magnetic core 200which receives a plurality of series connected windings, each of whichis composed of a plurality of turns.

Referring first to FIGURE 13, the voltage source E is connected acrossthe primary winding section 201, while the output voltage 9E is derivedlfrom the nine series connected turns illustrated. Clearly, a current ofthe magniture 91 must be drawn from the voltage source E. This currentless the magnitude 1I flows in the primary winding 201, thus causing anet current 8l for driving flux in core`200. The two additional turns ofthe first section will each have an upwardly directed current I so thatfor the rst group of three turns, there is a net downwardly directedcurrent 6I.

In the next two groups of three turns each, each turn supplies themagnitude 1I in an upward direction, thus providing the opposing current6I for a net zero value of ampere turns for the core 200. That is, thenet current for each group of turns is not zero, but is some discretevalue.

As indicated in FIGURE 13, a leakage liux will be created by the currentmagnitude 6nI where n is the total number of turns.

With the arrangement of the invention, and illustrated in FIGURE 14,leakage flux will be canceled within each of the groups of turns so thatthere will be smaller leakage g flux and thus a lower reactance for thetransformer system. Thus, FIGURE 14 illustrates four groups of windingswhich are cascaded in accordance with the invention on the common core260.

In the first and lower group of turns, the central conductors provide 7Iand 1I, respectively, to counterbalance the 3l of the input winding 11.Thus, there is a net zero current for the first group of windings. In asimilar manner, the net current in each of the additional Winding groupsis zero, as shown in FIGURE 14.

Accordingly, the invention provides cancellation within each windinggroup so that the leakage flux around the core is substantially reduced,thus leading tota much lower reactance device.

Where coaxial cable is used to define the windings of FIGURE 14, it willbe apparent that the coupling between adjacent turns is much tighter andthe induced current between winding sections will be much more exact.Therefore, the net current will be more nearly zero than when using astandard transformer winding.

While the present invention is particularly applicable to cases wherethe transformer System is to have a substantially zero leakagereactance, it is to be understood that the invention is additionallyapplicable to those cases wherein some minimum leakage reactance ispermissible so that coaxial cable is not necessary. That is to say, theinvention is applicable to other types of conductor arrangements otherthan coaxial arrangements.

By way of example, and as is Vschematically shown in FIGURE 10, atransformer corel may have a winding formed of adjacently positionedaxially elongated or sheet conductors 151 through 161 where conductor161 is the nth conductor or middle conductor of the pack, correspondingto the middle conductor of a coaxial cable. Conductors 151 and 160correspond to the sheath.

The windings 151 and 160 may, for example, be primary windings, whilewindings 152 through 159 and 161 are secondary windings with thecomplete schematically illustrated group of windings being wound at oneand the same time, as is the case in the coaxial type of conductor. Notethat in FIGURE 10 I show an equivalent of a cross-sectional view throughthe combined conductor forming six windings, and that this group will bewound around a transformer core such ascore 150.

The conductors 151 through 155 are further connected in parallel withconductors 160, 159, 158, IS7 and 156 respectively with transportationsbeing used throughout the Winding, if desired. To assure a more uniformdistribution of current, although the distribution of current obtainedfrom a continuous winding of the type of FIG- URE 10 will be suicientfor most cases.

When the transformer conductor is constructed in the manner shown inFIGURE l0, a transformer system may be seen to be formed in the mannerillustrated in FIG- URES 7 and 8, whereby a high voltage ratio may beprovided for the system without requiring either an excessively largenumber of parallel conductors within the cable or without requiring anexcessively large voltage between the adjacent conductors of the unitaryconductor bundle.

Where requirements are less stringent so far as leakage reactance isconcerned, a one-sided arrangement, schematically illustrated in FIGURE11, may be used where the cable is composed, as schematicallyillustrated for the cable cross-section, of only conductors 151 through155 and 161.

FIGURE 12 illustrates one manner in which a stepdown transformer can bemade using a winding of the type shown in FIGURE 11, and applying theconcepts of cascaded systems, as described in FIGURE 8. Thus, in FIGURE12, a common transformer core 162 is Wound with three sections ofwindings, 163, 164 and 165 respectively which are each, in turn, formedof three layers of windings, as contrasted to the two layers shown inFIGURE 8. Thus, section 163 is formed of three layers 166, 167 and 16Swhich are, in turn, composed of five layers of sheet metal or foilseparated by sheets of insulatinfr material (not shown).

Each of the groups of layers, such as layers idd, M7 and ldd, are woundas a unitary conductor bundle to simultaneously form the primary andsecondary windings of the transformer. Clearly, there will be aninter-layer insulation between layers, as indicated by dotted lines la@and i7@ for section M3, while section insulation is provided asillustrated in the double dotted lines such as lines il'l betweensections 163 and ldd.

lt will be noted that FGURE l2 results in a transformer that resemblesone having interleaved primary and secondary windings. lt differs,however, in that the full voltage of the primary winding of thetransformer does not appear across the insulation between primary andsecondary windings.

These spaces need only be sufficient for a relatively small portion ofthe voltage, and for ventilation purposes. Therefore, they do notcontribute appreciably to the irnpedance as in the standard interleavedtransformer.

The sheet-type conductor construction of FIGURE 12 is particularlyuseful for moderate and low voltage transformers having large turnsratios, as, for example, is required in spot-welding type transformers.ln such application, the input AC. generator E72 is connected, asillustrated, with the load V13 being connected as shown. The load f7.3,for example, can be the electrodes of a spotwelding transformer.

Although l have described preferred embodiments of my novel invention,many variations and modifications will now be obvious to those skilledin the art, and I prefer therefore to be limited not by the specicdisclosure herein but only by the appended claims.

I claim:

1. A high voltage transformer system; said high voltage transfer.; ersystem comprising a plurality or" Windings and a common magnetic corereceiving said plurality of windings; each of said plurality of windingscomprising a plurality of turns; each of said plurality of windingshaving an input winding portieri; each of said plurality of windingsexcept the last of said plurality of windings having an output windingportion; the said input winding portion of each of said plurality ofwindings being connected in series with the said output winding portionof the next adjacent winding of said plurality of windings.

The device substantially as set forth in claim l, wherein said inputwinding portion of the iirst of said plurality of serially arrangedwindings defines the input connection for said system; the outer ends ofsaid plurality of windings dening the output terminals of said system.

3. rl`he device substantially set forth in claim l. wherein each of saidwindings comprise coaxially arranged conductors; each of said coaxiallyarranged conductors sequentially connected to one another to denne aplurality of turns equal in number to the number of turns of saidwinding around said core times the number of coaxially arrangedconductors.

References Cited bythe Examiner UNITED STATE-S PATENTS l,ll7,293 ll/l4Wilson 307-17 X 1,523,367 1/25 Petersen et al. 307-17 1,868,483 7/32Austin 307-17 3,995,965 10/61 Wertanen 336-195 10i-IN F. BURNS, PrimaryExaminer.

MlLTON O. HRSHFIELD, LLOYD M. MCCOLLUM,

Examiners.

1. A HIGH VOLTAGE TRANSFORMER SYSTEM; SAID HIGH VOLTAGE TRANSFORMERSYSTEM COMPRISING A PLURALITY OF WINDINGS AND A COMMON MAGNETIC CORERECEIVING SAID PLURALITY OF WINDINGS; EACH OF SAID PLURALITY OF WINDINGSCOMPRSIING A PLURALITY OF TURNS; EACH OF SAID PLURALITY OF WINDINGSHAVING AN INPUT WINDING PORTION; EACH OF SAID PLURALITY OF WINDINGSEXCEPT THE LAST OF SAID PLURALITY OF WINDINGS HAVING AN OUTPUT WINDINGPORTION; THE SAID INPUT WINDING PORTION OF EACH OF SAID PLURALITY OFWINDINGS BEING CONNECTED IN SERIES WITH THE SAID OUTPUT WINDING PORTIONOF THE NEXT ADJACENT WINDING OF SAID PLURALITY OF WINDINGS.